440 Head and cam question

-

Mopower71

Speed Demon
Joined
May 31, 2004
Messages
2,183
Reaction score
39
Location
Poughkeepsie, N.Y.
1968 stock short block with 516 closed chamber heads.
Would there be a gain in anything if I switch to a set of 906's ?
I know there will be a loss in compression, but will the port/valve size make a difference?

What is the largest cam, lift/duration, that can be run with out interferance?
Stock '68 flat top pistons, with no valve releifs.
 
the 906 head will flow a lot better than a 516 head. you can cut the head surface .025 ,will help with comp. a motor is an air pump, more air in= more power. as for duration, mopar states stay under 280 advertised duration. look at your 906 head, under side is casting number, next to it is a letter. should be a M,R or F. the F is the better flowing casting. the M is next best.
 
Depending on what you're doing, it may be a wash. The 906 exh port is better, the exh valve is bigger, and the intake flows a little better. It's going off an article I read somewhere else, but the 516s dont flow as well, mainly at lower lifts. There is less than 11% in that article difference between the two at max cfm, but the 906 flows 6% more by .300 lift. That's where the typical street cams make or break you. You'll be giving up an across the rpm band power loss with the compression drop, but that's not like 2 points..It's only about 1/2 a point. I guess if the cam is smaller, and a modern grind (like fast rate of lifts..) then you may notice a little gain. Mill the 906s a bit, and you'll see more like they said...
 
I am building a 440 now with the 516 closed chamber heads, I have used the 2.14 intakes , the 1.81 exhaust valves and opened the pockets to the bottom of valve seat, Ports were massaged, the exhaust is really bad with that lump just under the valve seat, I "massaged " that really well. milled .030, I will be using a comp cams 222@.050Intake and 226@.050 exhaust with .467 lift, with the stock upswept design 6 pack ex manifolds, I have gasket matched all the ports . the intake is a alum 6 pack set up. I am looking for this car to SCREAM with it 4:10 axle....good luck
 
Not to "brag", well just alittle, i've gone a best of 10.91@122.71 with BONE STOCK 906s, they CCed at 90, this is in a 3100 lb. duster, 451, 9.8.1 compression, 250/256@ 50 comp solid, 511/517 Net lift, 411s, 4100 stall, M1, 750 carb, shifting at 5800, This was on a slow 1.58 60ft. I'd say there not too bad!
 
-
Back
Top